[what]

For math, I find it's all practice. You have to do lots of problems, which isn't really possible in a short period of time. Always do all your homework, spreads your studying through the year and exam/test questions will be similar to ones you have seen already. I also don't like to study last minute, better to get a good night's sleep.

For everything else, I would say write a cheat sheet (not to use). The act of writing forces the information through your brain and out your hand.

EDIT: should add, when you're actually writing the exam, read all the questions first. Then start with the the ones you know right away. If you have to think, come back to it later.